Binding of 2,4-dinitrophenyl derivatives by the light chain dimer obtained from immunoglobulin A produced by MOPC-315 mouse myeloma.

The light chains, but not the heavy chains, obtained from immunoglobulin A produced by the MOPC-315 mouse myeloma bind the 2,4-dinitrophenyl (DNP) group. Specific interaction with the DNP group was determined by using several immunoadsorbents, including DNP-L-lysine-Sepharose, and elution of the adsorbed light chain by DNP-glycine. Equilibrium dialysis experiments showed that the M-315 light chain in the form of dimer (45 260 daltons) has two identical and homogeneous binding sited that bind DNP-L-lysine with an intrinsic association constant of 6.3 x 103 M-1. This is the first report, to our knowledge, in which the light chain binding data permit reliable determination of the binding constant and valency of the isolated light chain, and which suggests a predominant role for the light chain in construction of the binding site in the intact immunoglobulin molecule.